Method and apbabattts fob igniting combustible mixttlbbs



March 21, 1933. G, (1 M ET AL 1,902,541

METHOD AND APPARATUS FOR IGNIZTING COMBUS'IIBLE MIXTURES Filed April 15,1931 2/ INVENTOR- BY ma ATTORNEYS.

'the character indicated, and to Patented Mar. 21, 1933 UNIT D-- STATESPATENT OFFICE GEORGE G. BROWN AND MOTT SOUDERS, JR., ARBOR, MICHIGAN Vmnon AND APPABATUS ron IGNITING comaosmnn mm Application filed April 15,

inflammation of combustible mixtures without, developing undesirablephenomena, particularly' s waves, and to provide suitableapparatus foraccomplishin such end. More specifically, it is an obJect of theinvention to' prov1de a method of effecting combustion incombustionchambers of the character indicated without 7 the development oftraveling pressure phenomena of rovide means for eliminating orsubstantia ly suppressing vibrations or oscillations of appreciableamplitude'in the traveling flame and in conjunction with the ignitingagent. A further ob'ect of the invention is to provide-means orcontrolling .the duration and intensity of i nition, articularly theduration of the e ecti'ic discharge which ignites the combustiblemixture in acombustion chamber.

Other objects of the invention will in art be obvious and'will in partappear ereinafter. I

The invention accordingly comprises the several steps and therelation-and order of one or more of such steps with respect to ,each ofthe-others, and the apparatus embodying features of construction,combination of elements and arrangement of parts which are adapted toeffect such steps, all as exemplified in the following detaileddisclosure, and 'the scope of the application of which will beindicatedin the claims For a fuller understanding of the nature and objects ofthe invention, reference should taken in connection with theaccompanying drawing, in which:

Fig. 1 shows an oven provided with an lpngated combustion chamberadapted for tltespractice of the present invention; Fig. 2 is aviewpartly inplan and partly be had to the following detaileddescription 1931. Serial No, 580,270.

cated in Fig. 2 in accordance with the present invention.

In the industrial arts, it is frequently de- 50 sirable to enerate largequantities of heat in relative y small spaces'and in relatively shortperiods of time. The time interval permitted in many instances is soshort that it is conventionally described as instantaneous. Thegeneration of heat in this manner is required in various types ofdevices, for example, in heat engines, in internal combustion engines,in certain forms of ovens and in intermittent heating devices. It hasbeen customary where space limitations are essential to emplocombustible mixtures as the medium supp ying the heat which'are ignitedby any suitable means, for example, by a hot spot or by the passage ofan electric spark.

While the liberation of heat under such circumstances may be saidtoapproach the instantaneous, it is known that there is a definite rateof combustion of the combusti- 30 ble mixtures in closed chambers, whichrate is-determined by several factors, for example by the pressure, bythe presence of foreign agents, and by the character ofthe ignitingagent; When combustion of combustible mixtures is initiated in a localportion thereof, inflammation is propagated throughout the mixture at adefinite rate, while accompanied by other phenomena, some of whicl areof a highly detrimental character, for example, the shock and intensetraveling pressure waves, accompanying the flame propagation.

The pressure waves normally developed in explosive mixtures of the,character indicated, for example in a mixture of hydrocarbon vapors andair, travel with velocities of an order equal to that of [s ound, and ithas been ascegtained that the have an accelerating effect on the rate 0inflammation accompanied by a rise of pressure. It has beenobservedfthat when suchwaves exceed a predetermined minimum amplitude,the rate of'rise'of pressurev is affected by the presence of certainforeign agents, for example the rate is 'frequentl increased bytetra-ethyl lead, when intro uced in vapor form with the fuel va or.Where the waves are small of amplitu e, the tetra-ethyl lead has beenobserved to decrease the rate of rise-of pressure in the combustioninduced b such waves. It is not easy, however, to

distinguish between the rate of rise of pressure in such combustion andthe rate of reaction in anormal flame where induced by pressure waves.Decomposition of the foreign agent has been roposed to effect control,but it has been etermined that decomposed tetra-ethyl lead will noteliminate sound velocity waves under all practical conditions -incombustion of this character. The development of such waves into apressure wave of. relatively great am litude, or socalled shock wave,has been '0 served within certain limits under such'circumstances. It isseen in consequence that such agents are not suflicient means forcontrolling, compen-.

eating for, or eliminating the nomena referred to above. We haveascertained that the undesirable undesired phephenomena accompanying theinflammation I of combustible mixture are influenced, not

caseas a single direct discharge without onlyby the character andintensity of the ign ting agent, but also by the time and manner ofapplication of the igniting agent. Where an electric discharge 1s.theignitin agent this should be app ied in the idea nition be limited to amaximum duration which is usually'a small fraction of a second anddependsupon' the intensity of discharge, the frequency of oscillationand the degree of damping in the circuit, and the characteristics of thecombustible mixture and the combustion chamber. .For example satis-'factory results may be obtained and the presence of shock wavesavoidedif the duration of ignition be 0.025 seconds covering 1.5 cycles of a(SO-cycle damped discharge, when igniting hydrpcarbon vapor-air mixturesat atmospheric temperature and pressure in a relatively large closedcombustion chamber,

atmospheres and a such as one 30 inches in length and 3 inches indiameter, which may be completely inflamed in 0.16 seconds afterignition. On the other hand, violent shock waves which will rupture thesame a paratus are developed by simply increasing the number ofdischarges across the spark gap so asto y cupy a timeinterval of about0.15 seconds.

As the rate of reaction is increased by an increase in pressure ortemperature, it is necessary to decrease proportionally the duration ofcontact between the explosive mix-- ture and the electric ignitingdischarge. For example, the contact should be for about oneten-thousandth part of a second where the combustible mixture is' ofhydrocarbon vapor and air at a pressure upwards of 5 200 degrees F.

In accomplishing combustion in accordance with the present invention,the commanner and brought to the desired condition of temperature andpressure without effecting ignition. This is 'then effectedindependently by suddenly applying an igniting temperature upwards of'bustible mixture is provided in the, usual agent, such as an electric sark directly as a substantially unilateral 'd1scharge-2for the desiredbrief interval of'time. Where an electric sparkis the igniting agent,any suitable electrical system may be employed for applying the'sparkwhere its character and duration are determined by the electricproperties of the system. A revolving commutetor in conjunction with adamping circuit has been. found suitable for controlling the duration ofthe discharge in relatively slow burning mixtures such as hydrocarbonvapor and air at substantially atmospheric pressure. 1

In the accompanying drawing is illustrated a practical manner in whichcombustion is effected by an electric spark in accordance with thepractice of the invention. Here denotes an oven which is to be heated bythe combustion that takes place in an elongated combustion chamber 11,here shown in the form of a sinous pipe disposed near the top of theoven. Th s pipe, as shown in Fig. 2, has a valved connection 12 foradmitting and discharging at will gaseous agents to and from theinterior of the chamber.

Electric means for eflecting ignition in the manner above indicated areshown at the left of the drawing in Fig. 2, where 13 denotes acommutator adapted to revolve at a relatively high rate of s eed. Thiscommutator 'is shown as provide with a contact segment 14 made to span arelatively short are, which when revolved operates to reduce the timefor the passage of the spark to the desired,

short interval. A conductor 15 leads from the commutator to an electrode16 of a spark gap within the combustion-chamber The 65 chamber, since aother electrode 17 of this ga has a conductor 18 in series with an inuctance coil 19 and the contact 20 which bears on the commutator 13 andis adapted to make contact with the segment 14 when it sweeps under thesame. This, system is arranged to be supplied with electrical energythrough the winding 21, which is inductively related to the winding 19,the winding 21 being connected to any suitable intermittent or periodicsource of electric current.

While a dischar e of suitable character and duration may ie pi'oduced.by an elec; trical system containing only inductance and a commutatorarranged for closing the circuit for but relatively brief intervals,other electrical systems may be em loyed. Figs. 3, lfiand 5show-exemplary orms of other electrical systems which may be substitutedfor that shown in Fig. 2. In Fig. 33 an inductance 29 is shown in serieswith the commutator 13, a condenser 24 and a,

spark gap 26-27. Here the condenser is shunted by The resistance, as isObVlOllS, infects the time constants ofthe circuit and operates toinsure the desired brief discharge, which is employed in the practice ofthe invention.

In the arrangement shown at Fig. 4, an inductance 39 is shown in serieswith a commutator 13 and a spark gap ,36-.37. The gap here is shuntedbacondenser 34 havlng in series therewit a high resistance 35 whichattenuatesthis spark and also affects the time characteristics: of thedischarge. Fi 5 shows another system similar to that in ig. 4,butdifiers therefrom in having a grounded connection 40 whereby arelatively constant spark characteristicis at all times denser-34 beingaccomplished outside of the mutator prior to the recharging stage. Thesystems shown in Figs. 3, 4 and 5 are arranged to be supplied withelectric l-energy through the windings 21 which are inductively relatedto' the. windings 29 and 39' respectively, the winding 21'beingconnected to any suitable intermittent or periodic source of electricalcurrent in a manner similar tothat shown in and described in rela-.

tion to Fig. 2. I

In operation, the chamber 11 isfilled with a combustible mixture at adesired pressure and temperature. The commutator 13 may be keptconstantly revolving if desired, so that when itis desired to ignite themixture the circuit containing winding'21 is closed. This effects thecombustion desired.

While a closed combustion chamber has been illustrateda's one to whichthe process of the present invention-is applicable, it is apparent thatthe' practice of the invention is not limited to such variety ofcombustion such a relatively high resistance 25. a

mixtures in combustion nsured; the complete discharge of thecon-.

, the accom animent of'shock .pheifes, and igniting the same b chamberthrough which the gaseous agents are adapted to flow may be employedeq'uall well. rate of fiow and the interval between the passage of theigniting spark are respec-. tively so timed that the chamber issubstantially filled with fresh mixturebefore firing. Since certainchanges in carrying out the above method and apparatus and in theconstructions set forth,.which embod the invention may be made withouteparting from its scope, it is intended that all matter contained in theabovedescription or shown in the accompanying drawing shall beinterpreted as illustrative and not in a limitin sense.

aving described our invention, what we claim as new and desire/co secureby Letters Patent, is: 1.The method of i iting combustible mixture incombustion c ambers'without the accompaniment of shock waves whichcomprises introducing a combustible. mixture within a combustionchamber, after igniting the same bythedirect application of. an ignitingagent for a period of time of the order of a ten thousandth ,part of asecond.

In such case, the.

and therev 2. The method of igniting combustible.

chambers withoutv h as it combustible mixture at a desired pressure andtemperature,

passage of an electric discharge for a relatively brief interval oftime. i

' 3. The method of igniting combustible chambers without theaccompaniment of shock waves which comprises filling a combustionchamber with a combustible mixture at a desired. pressure andtemperature, and igniting the same by a substantially unilateral passageof an electric spark for a. period of time not exceeding a smallfractionof a second.

-4.'.The method of ignitln'g combustible mixture in combustion chamberswithout waves which comprises lling a combustion chamber with acombustible mixture at a desired temperaseveral atmosture j and at apressure of a substantially unilateral passage of an e ectric spark ofdesired intensityt ior a period of time of the order of. aten-thousandth part of a second. i

5. The method of igniting combustible mixtures in combustion chamberswithout the accompaniment of shock waves 1 which comprises filling acombustion chamber with a combustible mixture containinghydrocarbdn'fuel vapors and air at a pressure of the order of severalatmos heres' and at a temperature below that o ignition, and ignit; ingthe same by a substantially unilateral and igniting the same by asubstantially unilateral passage of an, electric s ark of desiredindischarge to substantially unilateral tensity for a period of fame ofthe order of a ten-thousandth part of a second.

the ignition of I 6. Apparatus for efiecting combustible mixture withoutthe accompaniment of shock waves, comgerising in combination acombustion cham r having an inlet-and a discharge, and electric meansfor ignitin the mixture, said means being constructe to control theintensity of the igniting effect and to limit the time of itsapplication to a desired period.

7. Apparatus for effecting the ignition of combustible mixture withoutbeing accomnied by shock waves, comprising in comination, a combustionchamber having an inlet and a discharge, and an electric system arrangedto ignite the mixture in said chamber by the passage of an electricdischarge, said system including electric elements for controlling theintensity of said discharge and an element for limiting the assage for aperiod of time of the order 0 a tenthousandth part of a second.

8; Apparatus for eflecting the ignition of combustlble mixture withoutbeing accomanied by shock waves, comprising in comination, a combustionchamber having an inlet and a discharge, and an electric system arrangedto ignite the mixture in said chamber by the saidsystem inc udingelectric elements for contro ling the intensity of an igniting spark anda commutator for limiting the spark to substantially unilateral passagefor a period of time of the order part of asecond or less.

In testimony natures. I

' GEORGE G. BROWN. MOTT SOUDERS, Jn.

assage of an electric spark,

of a ten-thousandth whereof we aflix our sig-

